1. TECHNICAL FIELD
The present invention relates to an analog-digital converting method and an analog-digital converting apparatus for converting an analog signal into a digital signal.
2. RELATED ART
An N-way interleaved analog-digital converting method is known that involves using N analog-digital converters (referred to hereinafter as “ADCs”), when converting an analog signal into a digital signal, in order to increase the apparent sampling rate, as shown in Japanese Patent Application Publication No. 2000-346913, for example.
With this interleaved analog-digital converting method, however, the frequency spectrum of the digital signal cannot be accurately calculated if there is an error in the phase of the sampling clock provided to each ADC or in the frequency characteristics of the ADCs.
For example, the phase of the sampling clock provided to each ADC must be different for each ADC by a prescribed amount, and it is difficult to accurately shift the phase of the sampling clock by units of the prescribed amount. Furthermore, even when the sampling clock is provided to each ADC with the correct phase, variation in the gain or the sampling timing of the ADCs occurs if the frequency characteristics of the ADCs are not ideal, and this makes it difficult to accurately calculate the frequency spectrum of the digital signal.